CELSIUS
A scale on a thermometer where the interval between the boiling point and the
freezing point of water is divided into 100 degrees. Freezing point is
represented by 0 degrees and boiling point is represented by 100 degrees. The
same scale is also utilized in Centigrade.

DECAYING ORBIT
A path around an object which decreases in size with time. For example, when
a satellite enters a decaying orbit above Earth, its orbit size decreases to
the point that it enters Earth's atmosphere where it burns up.

ELECTROMAGNETIC SPECTRUM
The entire range of the different types of
electromagnetic radiation, or waves. It goes from the very long wave, low
frequency, radio waves through infrared waves and visible light waves to the
very high frequency and short waves of the gamma-rays and X-rays. Those wavelengths in the visible light range have a specific color associated with
them when they pass through a prism. The lower frequency, longer wavelengths
produce a red while those with higher frequency, shorter wavelengths
produce a violet. Those wavelengths which fall somewhere in between these two
points produce the orange, yellow, green, and blue also found in a spectrum.

ELECTROMAGNETIC WAVE
A wave of electric and magnetic energy that is generated
when an electric charge is accelerated.

KELVIN
A scale for measuring temperature where 0 Kelvin is equal to -273.16 degrees
Celsius. Zero Kelvin is referred to as absolute zero, the point at
which all motion within molecules comes to a stop.

MAGNETIC FIELD
The area in which an attractive or repelling force exists
between two magnets or in association with the element iron. The Earth's
magnetic field is thought to be due to the liquid iron-nickel which is in its
core. This magnetic field protects Earth from constant bombardment by
high-energy charged particles.

MANTLE
The middle layer of a planet located between the crust, or surface,
and the core.

MICROMETEOROID
Very small pieces of matter which are encountered in space.

MICROWAVE
Electromagnetic radiation which has a long wavelength (between
1 mm and 30 cm). Microwaves can be used to study the universe, communicate
with satellites in orbit around Earth, and cook popcorn.

QUANTUM MECHANICS
A theory in physics which is based on 2 ideas: (1) light can be emitted
or absorbed only in discrete quantities called quanta, whose energy is
proportional to their wavelength; and (2) you can never be exactly sure of
the position and velocity of a particle, the more accurately you know
the one, the less accurately you can know the other.

QUASAR
A distant energy source which gives off vast amounts of radiation,
including radio waves and X-rays.

RADIO WAVES
A type of electromagnetic radiation which has the lowest
frequency, the longest wavelength, and is produced by charged particles
moving back and forth. Radio waves are not blocked by clouds in the Earth's
atmosphere.

RETROGRADE
Having a direction which is opposite that of similar bodies.

SATELLITE
An object that revolves around a larger primary body. Satellites
may be naturally occurring, such as the Moon, or they may be man-made, such as
the Hubble Space Telescope and the Compton Gamma-Ray Observatory.

SOLAR ECLIPSE
A shadow which falls on an area of Earth when the Moon moves
between the Sun and Earth.

SOLAR FLARES
A magnetic storm on the Sun's surface which shows up as a sudden
increase in brightness.

SOLAR PROMINENCES
Gases trapped at the edge of the Sun which appear to shoot
outward from the Sun's surface.

SOLAR SYSTEM
The Sun and all of the planets, comets, etc. which revolve
around it.

SOLAR WIND
A continuous stream of charged particles which are released from the Sun
and hurled outward into space at speeds up to 800 kilometers per second.
Solar winds are very prominent after solar flare activity.

SOLAR WINGS
A panel of solar cells which converts sunlight into electrical
energy.

SPECTROGRAPH
The image of the electromagnetic spectrum produced by a spectroscope.

SPECTROSCOPE
An instrument which separates visible light into its various
wavelengths. Each wavelength corresponds to a specific color in the spectrum.

SPECTRUM
A band of colors which forms when visible light passes through a
prism. The band ranges in color from violet (shorter wavelength) to red
(longer wavelength).

SUNSPOT
A magnetic storm on the the Sun's surface which appears as a dark area. A
sunspot is approximately 1500 degrees Celsius cooler than it's surrounding
material. The number of sunspots we see on the Sun at any given time appears
to cycle every 11 years.

TECTONIC ACTIVITY
A shifting of an object's surface due to changes in the
material underlying the surface.

TELESCOPE
Any of various devices, sometimes made with an arrangement of lenses,
mirrors, or both, used to detect and observe distant objects by their
emission, transmission, reflection, or other interaction with
invisible radiation.